Ganymede #3 Proto-Earth

“The surface of Ganymede shares many similarities with Europa. Ganymede’s surface is also made of water ice, but unlike Europa’s surface, it shows signs of varying age. The darker regions are heavily cratered, suggesting they are billions of years old. The lighter regions show no signs of craters and it is thought that eruptions of water covered the surface before freezing over. These areas are geologically younger than the darker regions.
If liquid water occasionally makes its way to the surface to fill in craters, could that suggest a liquid ocean similar to the one that might exist on Europa?”

“Ganymede is the largest satellite in our solar system. It is larger than Mercury and Pluto, and three-quarters the size of Mars. If Ganymede orbited the sun instead of orbiting Jupiter, it would easily be classified as a planet.”

“Like Callisto, Ganymede is most likely composed of a rocky core with crust of rock and ice. Ganymede has had a complex geological history. It has mountains, valleys, craters and lava flows. Ganymede’s dark crust is mottled with bright spots where recent meteorite impacts have exposed clean bright ice from below the surface.”